CGRG Bibliography of Canadian Geomorphology
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Author : Bernier, F.; and Occhietti, S.
Date : 1991
Title : New lower glacial sequence of Saint-Pierre sediments, Sainte-Anne-de-la-Pérade, Québec. [Nouvelle séquence glaciaire antérieure aux sédiments de Saint-Pierre, Sainte-Anne-de-la-Pérade, Québec.]
Publication : Geographie physique et Quaternaire
Issue : 45(1):
Page(s) : 101-110
Abstract
New lower glacial sequence north of the St. Lawrence River, Sainte-Anne-de-la-Perade, Quebec. Three new units of glacial and glaciolacustrine origin, older than the St. Pierre Sediments, have been observed on the north shore of the St. Lawrence River between Sainte-Anne-de-la-Perade and Grondines. The lowermost till or Portneuf Till lies on the Ordovician bedrock and is covered by deglaciation varves or Deschambault Varves which represent at least 1000 years of sedimentation. The matrix of the lodgement till can be very calcareous with values ranging from 2% to 30% and has a variable texture. The directional data show a NNW to SSE trend. The age of Portneuf Till is uncertain; the till is related to one of the isotopic stages 4, 5b, 5d or 6. The intermediate diamicton or Sainte-Anne diamicton is intercalated between the Deschambault Varves (or the sand wich truncates them) and the stratified silts-La Perade Clay-St. Pierre Sediments sequence. This diamicton contains disc shaped calcareous concretions which are identical to the one found in the underlying varves. The fabrics indicate a random orientation of the stones. The sedimentary sequence of the Portneuf Till-Deschambault Varves and the Sainte-Anne diamicton represent either two separate glacial events or one major event with a late glacial phase. The Portneuf Till- Deschambault Varves sequence is similar to the ones at Cap Levrard and at the Riviere aux Vaches on the south shore of the St. Lawrence River. The correlation between these sequences is not yet demonstrated. The Portneuf Till is lithologically different from the Becancour Till and represents, with the Deschambault Varves, a stratigraphic reference on the north shore of the St. Lawrence River.
Bibliography of Canadian Geomorphology